The Cockeyed squid is one of the most peculiar species at the ocean. The most peculiar thing which always seeks scientists attention is the unequal shape of their eyes. Their one eye is black and small and the other eye is big and yellow. Now scientists are able to find the reason behind the different shape and size of the eyes. This second large eye helps them to catch their pray in the twilight zone of the ocean.

Duke University’s graduate student Kate Thomas graduate student Kate Thomas and her colleagues started watching more than 150 underwater videos on the Cockeyed squid. Those videos were captured by remotely operated vehicles (ROVs) from the Monterey Bay Aquarium Research Institute (MBARI) over the past 30 years. The creature uses it’s big eye to look upward and small eye to look downward. It swims in a strange upside down position, with its tail up and heads down. Heir findings were first published in the journal of Philosophical Transactions B.

Lead researcher Kate Thomas said in a statement,“Eyes are really expensive to make and maintain. You want eyes just big enough to do what you need to do, but you don't want to have any bigger eyes because then you are just wasting resources.” According to the Mail Online, during the birth, Cockeyed squids (Histioteuthis Heteropsis) has both eyes same. As they grow up, their left eye becomes bigger.

Live Science report says researchers came to the conclusion of “bioluminescent” because it is almost impossible to see downward with the sun's dim light shining above. Upside pointed eye improves the ability in dim light.

This visual adaptation is only for better visibility. Twilight zone ranges between the depth of 660 feet(200 meters) to 3,200 feet (1,000 meters) below sea level. As a very low amount of sunlight enters in this area that light makes the area dim and a monochromatic blue color. There are several species on Earth which adopted their bioluminescence to view in the twilight zone.